In one aspect, dynamic motion sensors are transducers used for measuring acceleration. Single axis or uni-axial dynamic motion sensors are generally sensitive along a single axis. For example, acceleration magnitude may be measured by means of an external instrument or measuring system sensing the electrical output of the accelerometer. The accelerometer output may be a voltage waveform proportional to the magnitude of the applied acceleration. Similarly, dynamic motion sensing devices such as velocimeters and dynamically responding displacement transducers may output a voltage waveform or generate current proportional to velocity.
A dynamic motion sensor to be tested is referred to herein as a Sensor Under Test or “SUT” and a high accuracy reference sensor is referred to as “REF.” ISO16063-21 is an ISO standard entitled Vibration Calibration by Comparison to a Reference Transducer. 
SUT and REF devices may be attached to a device capable of imparting harmonic motion at significant displacement. One such device is depicted in FIG. 1 and is referred to as a long-stroke shaker or long-stroke vibrator. During the calibration, the reference transducer is used to measure the applied acceleration. Both accelerometers output a time-varying electrical signal proportional to the magnitude of the acceleration to which the device is subjected. This time varying electrical signal may take the form of a voltage proportional to the magnitude, but it may also be in the form of a current, or charge proportional to the magnitude of acceleration.